Alfred Perlstein <bright(at)wintelcom(dot)net> writes:
>> Are there any portability problems with relying on shm_nattch to be
>> available? If not, I like this a lot...
> Well it's available on FreeBSD and Solaris, I'm sure Redhat has
> some deamon that resets the value to 0 periodically just for kicks
> so it might not be viable... :)
I notice that our BeOS and QNX emulations of shmctl() don't support
IPC_STAT, but that could be dealt with, at least to the extent of
stubbing it out.
This does raise the question of what to do if shmctl(IPC_STAT) fails
for a reason other than EINVAL. I think the conservative thing to do
is refuse to start up. On EPERM, for example, it's possible that there
is a postmaster running in your PGDATA but with a different userid.
> Seriously, there's some dispute on the type that 'shm_nattch' is,
> under Solaris it's "shmatt_t" (unsigned long afaik), under FreeBSD
> it's 'short' (i should fix this. :)).
> But since you're really only testing for 0'ness then it shouldn't
> really be a problem.
We need not copy the value anywhere, so as long as the struct is
correctly declared in the system header files I don't think it matters
what the field type is ...
regards, tom lane